Protease inhibitors are currently used to inhibit the HIV type 1 protease and suppress the proliferation of HIV virus in human T-cells. It has been suggested that calcium-activated protease could lead to breakdowns of cytoskeleton proteins and organelles, leading to cell death. We, thus, initiate this hypothesis-driven research project; we want to know if HIV type 1 protease could cause cytotoxicity and neurodegeneration, similar to the HIV envelope protein gp120, in the central nervous system. Full blown AIDS is often manifested in patients as dementia, delusion, depression, and other psychiatric problems, that may be the consequence of neurodegeneration caused by cytotoxic HIV protease and/or envelope protein gp-120. The proposed cytotoxicity of the HIV type 1 protease and the HIV envelope protein gp-120 will be examined in cultured neurons derived from human NT-2 cell lines and the murine brain, as well. HIV virus can not infest murine T-cells but HIV protease and gp-120 may cause injury to murine cells in the brain. One of the obvious experiments is to investigate possible protective effects of protease inhibitors, both in vitro and in vivo, if HIV protease indeed causes cytotoxicity and/or brain injury. Possible protective effects of sodium channel blockers or potassium channel openers on gp-120's neurotoxicity will be examined. We will also investigate whether S-nitrosothiols, the newly discovered antioxidants, are useful in protecting brain neurons or cells against injury induced by cytotoxic HIV peptides or proteins. In addition, we propose to employ molecular biological procedures to study whether calcium or other cofactors can activate this protease produced by HIV virus. We will also determine the active portion of the HIV type 1 protease by using synthetic mutant peptides and examining their effects on the permeability of calcium ions in human NT-2 cells. The outcome of this high-risk AIDS research project could add our understanding of cytotoxic mechanisms of HIV protease and envelope protein, especially in the neuronal system that is obviously affected by HIV virus. It might also lead to discovery of alternative treatments for protection of brain neurons and/or T-cells against cytotoxic effects and/or brain disorders caused by HIV.